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Holographic model for heavy vector meson masses
The experimentally observed spectra of heavy vector meson radial excitations
show a dependence on two different energy parameters. One is associated with
the quark mass and the other with the binding energy levels of the quark
anti-quark pair. The first is present in the large mass of the first state
while the other corresponds to the small mass splittings between radial
excitations. In this article we show how to reproduce such a behavior with
reasonable precision using a holographic model. In the dual picture, the large
energy scale shows up from a bulk mass and the small scale comes from the
position of anti-de Sitter (AdS) space where field correlators are calculated.
The model determines the masses of four observed S-wave states of charmonium
and six S-wave states of bottomonium with , 6.1 % rms error. In consistency
with the physical picture, the large energy parameter is flavor dependent,
while the small parameter, associated with quark anti-quark interaction is the
same for charmonium and bottomonium states.Comment: In V5 we just added some clarifying explanations about the model. 5
tables, no figure. Version published in Europhysics Letter
Holographic Picture of Heavy Vector Meson Melting
The fraction of heavy vector mesons produced in a heavy ion collision, as
compared to a proton proton collision, serves as an important indication of the
formation of a thermal medium, the quark gluon plasma. This sort of analysis
strongly depends on understanding the thermal effects of a medium like the
plasma on the states of heavy mesons. In particular, it is crucial to know the
temperature ranges where they undergo a thermal dissociation, or melting.
AdS/QCD models are know to provide an important tool for the calculation of
hadronic masses, but in general are not consistent with the observation that
decay constants of heavy vector mesons decrease with excitation level. It has
recently been shown that this problem can be overcome using a soft wall
background and introducing an extra energy parameter, through the calculation
of correlation functions at a finite position of anti-de Sitter space. This
approach leads to the evaluation of masses and decay constants of S wave
quarkonium states with just one flavor dependent and one flavor independent
parameters. Here we extend this more realistic model to finite temperatures and
analyse the thermal behavior of the states and of bottomonium
and charmonium. The corresponding spectral function exhibits a consistent
picture for the melting of the states where, for each flavor, the higher
excitations melt at lower temperatures. We estimate for these six states, the
energy ranges in which the heavy vector mesons undergo a transition from a well
defined peak in the spectral function to complete melting in the thermal
medium. A very clear distinction between the heavy flavors emerges, with
bottomonium state surviving deconfinemet transition at
temperatures much larger than the critical deconfinement temperature of the
medium.Comment: 20 pages, 7 figure
Superspace Formulation for the BRST Quantization of the Chiral Schwinger Model
It has recently been shown that the Field Antifield quantization of anomalous
irreducible gauge theories with closed algebra can be represented in a BRST
superspace where the quantum action at one loop order, including the Wess
Zumino term, and the anomalies show up as components of the same superfield. We
show here how the Chiral Schwinger model can be represented in this
formulation.Comment: 11 pages, Late
Decay constants in soft wall AdS/QCD revisited
Phenomenological AdS/QCD models, like hard wall and soft wall, provide
hadronic mass spectra in reasonable consistency with experimental and (or)
lattice results. These simple models are inspired in the AdS/CFT correspondence
and assume that gauge/ gravity duality holds in a scenario where conformal
invariance is broken through the introduction of an energy scale.
Another important property of hadrons: the decay constant, can also be
obtained from these models. However, a consistent formulation of an AdS/QCD
model that reproduces the observed behavior of decay constants of vector meson
excited states is still lacking. In particular: for radially excited states of
heavy vector mesons, the experimental data lead to decay constants that
decrease with the radial excitation level.
We show here that a modified framework of soft wall AdS/QCD involving an
additional dimensionfull parameter, associated with an ultraviolet energy
scale, provides decay constants decreasing with radial excitation level. In
this version of the soft wall model the two point function of gauge theory
operators is calculated at a finite position of the anti-de Sitter space radial
coordinate.Comment: Shorter (letter) version. Results unchanged. More references
included. We now explain that the large UV scale of the model is associated
with the non-hadronic decay of the heavy vector meson into light leptons.
Version Published in Phys. Lets.
Axial Anomaly from the BPHZ regularized BV master equation
A BPHZ renormalized form for the master equation of the field antifiled (or
BV) quantization has recently been proposed by De Jonghe, Paris and Troost.
This framework was shown to be very powerful in calculating gauge anomalies. We
show here that this equation can also be applied in order to calculate a global
anomaly (anomalous divergence of a classically conserved Noether current),
considering the case of QED. This way, the fundamental result about the
anomalous contribution to the Axial Ward identity in standard QED (where there
is no gauge anomaly) is reproduced in this BPHZ regularized BV framework.Comment: 10 pages, Latex, minor changes in the reference
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Oxidative stress specifically downregulates survivin to promote breast tumour formation.
BackgroundBreast cancer, a heterogeneous disease has been broadly classified into oestrogen receptor positive (ER+) or oestrogen receptor negative (ER-) tumour types. Each of these tumours is dependent on specific signalling pathways for their progression. While high levels of survivin, an anti-apoptotic protein, increases aggressive behaviour in ER- breast tumours, oxidative stress (OS) promotes the progression of ER+ breast tumours. Mechanisms and molecular targets by which OS promotes tumourigenesis remain poorly understood.ResultsDETA-NONOate, a nitric oxide (NO)-donor induces OS in breast cancer cell lines by early re-localisation and downregulation of cellular survivin. Using in vivo models of HMLE(HRAS) xenografts and E2-induced breast tumours in ACI rats, we demonstrate that high OS downregulates survivin during initiation of tumourigenesis. Overexpression of survivin in HMLE(HRAS) cells led to a significant delay in tumour initiation and tumour volume in nude mice. This inverse relationship between survivin and OS was also observed in ER+ human breast tumours. We also demonstrate an upregulation of NADPH oxidase-1 (NOX1) and its activating protein p67, which are novel markers of OS in E2-induced tumours in ACI rats and as well as in ER+ human breast tumours.ConclusionOur data, therefore, suggest that downregulation of survivin could be an important early event by which OS initiates breast tumour formation
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